package LeetCode_Section;

import java.util.ArrayList;
import java.util.List;

//反转单链表
public class ReversalSingleLinkedTable {
    public static class ListNode {
        int val;
        ListNode next;

        ListNode() {
        }

        ListNode(int val) {
            this.val = val;
        }

        ListNode(int val, ListNode next) {
            this.val = val;
            this.next = next;
        }


    }


    class Solution {
        public ListNode reverseList(ListNode head) {

            //没有 或 只有一个
            if (head == null || head.next == null) {
                return head;
            }

            ListNode pre = null;
            ListNode cur = head;
            while (cur != null) {
                ListNode last = cur.next;
                cur.next = pre;
                pre = cur;
                cur = last;
            }
            return pre;
        }
    }

}
